Regenerative telegraph repeater utilizing an impulse generator



Nov. 8, 1949 w. T. REA 2,487,181 REGENERATIVE TELEGRAPH'REPEATERUTILIZING AN IMPULSE GENERATOR Filed June 3, 1947 5 Sheets-Sheet l [.761ourc'ollva 2/ LINE T 32 INCOMING LINE INVENTOR n! 7. REA

' AT7' R/VEV Nov. 8, 1949 w. T. REA 7 2,487,181

REGENERATIVE TELEGRAPH REPEATER UTILIZING AN IMPULSE GENERATOR FiledJune 3, 1947 3 Sheets-Sheet 3 FIG. J

sunli- 'I/ I2 7 a l RECEIVED SIGNAL POTENTIAL OF POM/Th.) RELATIVE TOP0/NT() OF FIG. 2 v

| FIG. 7 J

srnnr I 2 RETRANSM/TTED SIG/VAL /N 5 N TOR W TREA ATTO NE! Patented Nov.8, 1949 REGENERATIVE TELEGRAPH REPEATER UTILIZING AN IMPULSE GENERATORWilton "1. :Rea, vManhasset, N. Y., assignor to Bell TelephoneLaboratories,

Incorporated, New

York, N. Y., a corporation of New York Continuation of abandonedapplication Serial No. 545,781, July 20, 1944. This application June 3,1947, Serial No. 752,248

9 Claims. (01. 178-70) This invention relates to telegraph apparatus andsystems and particularly to regenerative telegraph repeaters.

This application is a continuation of copending application Serial No.545,781, filed .July 20, 1-944, now abandoned, which in turn is .acontinuation in partoi copending application-Serial.No. 460,948, filedOctober 6, 1942, now Patent- 2,454,-089, by W. T. Rea and J, .R.Wilkerson.

An object of the invention is to time the retransmission of telegraphimpulses by electronic discharge tube means, thus dispensing withmechanical distributors.

Another object of the invention is to initiate and terminate the cyclesof signal regeneration by electronic discharge tube means, thusdispensing with electromagnetic relays to perform this function.

One embodiment of the invention features a hot cathode gas-filledelectron discharge tube for initiating cycles of signal regeneration.

Another embodiment of the invention features a cold cathode gas-filledelectron discharge tube for initiating and terminating cycles of signalregeneration.

In accordance with both embodiments of the invention a signal receivingrelay deactivates a normally operative electron discharge device whichsets in operation an oscillatory circuit. The oscillatory circuitgenerates alternating current and the successive cycles of alternatingcurrent produce impulses at intervals equal to the telegraph impulseintervals of perfectly timed telegraph signals. These impulses seek toactiveto the deactivated one of two electron discharge devices, one orthe other of which is always conductive, and the receiving relay whichis under the control of receivedsignals determines whether or not thethen deactivated electron discharge device shall be activated. Each ofthe electron discharge devices upon ;being so activated quenches theother, and a signal transmitting relay is controlled in accordance withthe activation of the newly activated electron discharge device.

In accordance with one embodiment of the invention impulses generated bythe oscillator and rectified are impressed upon a condenser whichcontrols the grid ofan electron discharge tube and when the condenserhas received impulses equal to the number of impulses contained in thesignaling code upon which the system is operable the condenser ischarged sufiicien-tly to render the associated grid controlled electrondischarge tube conductive, which reactivates the electron discharge tubeinitially deactivated by the receiving relay which in turn deaotivatesthe oscillator, thus restoring the system to normal.

In accordance with another embodiment of the invention a condenser isassociated with, a resistor included in the anode-cathode circuit of theelectron discharge tube initially deactivated by the receiving relay.This tube is a hot cathode gas-filled electron discharge tube and thecondenser places a negative potential on the grid of this tube withrespect to the cathode so that upon the deactivation of the tube thegrid will prevent the immediate reactivation of the tube. The resistorassociated with the condenser has a sufficiently high resistive valuethat the discharging of the condenser to a potential at which the gridof the tube can reactivate the tube will require an interval equal tothe length of the signaling code upon which the system is operable. Uponbeing discharged to this potential the condenser permits the grid toreactivate the tube which in turn deactivates the oscillator, thusrestoring the system to normal condition.

In the first described embodiment of the invention the normallyconductive oscillator controlling tube which is deactivated by thereceiving relay in response toa signal, is a cold cathode gas-filledelectron discharge tube and the timing circuit which controls itsreactivation is arranged to impress a potential difference between thecontrol anode and the cathode of sufficient magnitude to break down thecontrol gap and thereby ionize the tube. .In the second describedembodimentof the invention the tube which controls the activation anddeactivation of the oscillator is a hot cathode gas-filled electrondischarge tube controlled by a grid and the timing circuit comprisingthe condenser and resistor is arranged to permit the grid to approachthe potential of the cathode and the limit of this approach is equalitybetween the potentials of the grid and the cathode. The tube will bereactivated when or slightly before this condition of equality isreached.

For a complete understanding of the invention reference may be had tothe following detailed description to be interpreted in the light of theaccompanying drawings wherein:

Fig. 1 is .a schematic circuit diagram showing that embodiment of theregenerative repeater which employs a cold cathode gas-filled electrondischarge tube for activating and deactivating the oscillator;

Fig. 2 is a schematic circuit diagram showing the alternative embodimentof the regenerative repeater which employs a hot cathode gas-filledelectron discharge tube for activating and deactivating the oscillator;

Fig. 3 is a diagrammatic representation of a portion of a receivedpermutation code telegraph signal having distortion;

Fig. 4 is a diagrammatic representation of the voltage across a resistorin the timing oscillatory circuit of Fig. 2 during oscillation;

Fig. 5 is a diagrammatic representation of the voltage produced bycondenser discharge across a resistor of Fig. 2 connected to theoscillatory circuit;

Fig. 6 is a diagrammatic representation of the combined efiect oralgebraic summation of the voltages represented in Figs. 4 and 5; and

Fig. 7 is a diagrammatic representation of the retransmitted signal.

Referring now to the drawings, and particularly to Fig. l, the referencenumeral II designates a polarized receiving relay which has operatingand biasing windings. The operating winding has one terminal connectedto grounded battery I2 and the other terminal connected to receivingtelegraph line I3. The biasing winding of relay I I has one terminalconnected to grounded battery I2 and the other terminal connected toground. The operation of relay I I is such that when line I3 is in themarking condition the armature of the relay engages the upper or markingcontact which has been designated M and when line I3 is in spacingcondition the armature engages the lower or spacing contact which hasbeen designated S.

The marking and spacing contacts of relay II are connected throughresistors I4 and I5, respectively, to the control anodes of cold cathodegas-filled electron discharge tubes I1 and I8, respectively. The cathodeof tube I1 is connected to one terminal of the right-hand winding of atransmitting relay I9, the other terminal of which is connected toground and this winding, when energized, causes the armature of therelay to engage the upper or spacing contact which has been designatedS. The cathode of discharge tube I8 is connected to one terminal of thelefthand winding of transmitting relay I9 and this winding whenenergized operates the armature of the relay to the lower or markingcontact which has been designated M. From this it will be apparent thattube I'I operates relay I9 to drive its armature to spacing and tube Ilmay be designated as the spacing control tube whereas tube I8 whenconductive drives the armature of relay I9 to marking and may bedesignated as the marking control tube. The marking and spacing contactsof relay I9 are connected to positive and negative batteries,respectively, and the armature of the relay is connected to transmittingline conductor 2 I.

The main anodes of tubes I1 and I8 are connected through individualresistors 22 and 23, respectively, and through common protectiveresistor 24 to the positive terminal of battery 26, the negativeterminal of which is grounded. Also, a condenser 21 is connecteddirectly between the main anodes of discharge tubes I1 and I8. Themanner in which tubes I1 and I8 control transmitting relay I9 will bedescribed later.

The armature of receiving relay II is connected by conductor 28 throughdropping resistor 25 and protective resistor 29 to the negative terminalof battery 3|, the positive terminal of which is connected to ground. Aconductor 32 extends from the marking contact of receiving relay I Ithrough resistor 33 to the cathode of a cold cathode gas-filled electrondischarge tube 34. The main anode of discharge tube 34 is connectedthrough conductors 31 and 38, left-hand inductance winding 39 and inparallel therewith through the series of resistors M and 42, and iinallythrough the right-hand inductance winding 43 to ground, which is at thesame potential as the positive end of battery 3|. When the system is inthe idle condition as shown with the armature of receiving relay II onthe marking contact, electron current flows from the negative terminalof battery 3| over the circuit previously traced to the cathode of tube34, through the discharge path to the anode of tube 34, and over thecircuits just traced to ground on the right-hand inductance winding 43and to the positive terminal of battery 3|.

Resistor 42 is employed as a potentiometer and its movable contact isconnected to the grid of the left-hand triode of a twin triode dischargetube 46. The cathode of the left-hand triode is connected throughresistor 41 to the point of interconnection of inductance windings 39and 43. Thus a portion of the voltage appearing across the winding 39 ofthe inductance is applied to the grid of the left-hand triode of tube46. The flow of plate current in resistor 41 applies a positivepotential to the cathode of this triode. Due to the low resistance ofthe inductance coil, the flow of current in tube 34', passing throughthe inductance, causes only a small negative voltage to appear on thegrid of the left-hand triode of tube 46. This is insuflicient to cut offthe flow of steady plate current.

Connected to conductor 31 and thus to the left-hand end of inductancewinding 39 are the contact arms of four multiple contact switches 5|,52, 53 and 54. The contact arms of switches 51 and 52 are ganged forconcurrent operation and the contact arm switches 53 and 54 are gangedfor concurrent operation. The contacts of switches 5 I, 52, 53 and 54are connected in various combinations to one side of capacitances ingroups 55, 55 and 51 and the other side of each of the capacitances inthe three groups is connected to ground. By the manipulation of switches5|, 52, 53 and 54 various combinations of capacitances may be connectedin parallel between conductor 31 and ground to provide a singleresultant capacitance value, and the condensers are so arranged withreference to switches 5!, 52, 53 and 54 that switches 53 and 54 providecoarse or relatively important changes in the resulting capacitancevalue and switches BI and 52 provide fine or minor changes in theresulting capacitance value. Since various combinations of parallellyconnected condensers are connected between conductor 31 and ground underthe control of the switches and since inductance windin s 39 and 43 areconnected between conductor 31 and ground, the condensers are inparallel with the inductances, which establishes an oscillatory circuit.Furthermore, since the grid of the lefthand triode of tube 46 isconnected to one end of this oscillatory circuit through resistor IIIand potentiometer 42 and since the cathode of the lefthand triode isconnected to a point intermediate the ends of the inductive branch ofthe circuit through resistor 41, the system comprises an electrondischarge tube oscillator which will generate oscillatory current, aslong as tube 34 is nonconducting at a frequency. determined by theadjustment of switches SI, 52, 53 and 54. These switches are in practiceadjusted so that the frequency of oscillations generated is twice thesignaling frequency and each cycle of oscillation is the e de tien a asome? i fi lill xim bulge trfiherfi deruepn wh ch h st m is up 1 51018.-ilheanode of the left-handtriode of I. i rounde A. p0

1 r;.pa a 1 e w ot nt cmetet" as insta ent he; s ill t arer ocad isted ta h teu t.. rio m. nd m di o c, ens as. e. onfieu at qapi he circ itissue that 1 eti Hi el on9 ste tinsi iems and. i V 1 1.815 P 2 13125?ail firll uw fii i gicyt szare -Rtdhf 'iullem lituda .T operatinsi-c aact istics of an oscillator of the typei shown eit ietare .fl y isclp edi copendine applicape eiafizatled February... 2.8,. .l29 4.2 93" Pa en 3.3 Q 6i ;;;1 nt d March? 6312945, by isa Wald} R- Wi e on and thedisclosure his cop ending applicatiOn; is incorporated here n by Ireference as; part of the present I L 1,.5: j i "1 cathode voltage forthe right-hand triode on of -tube 4 6 isderived from the adjustablecontact of -potenti0mfi6n5fi and the. plate voltage for,.,thi s triode,section K is; derived. from the. ad justable contact of potentiometer 63The anode circuit; of the right-handtriode of tube int clues the.primary. ,winding .of a transformer fia which is shuntedby-aresistor-E1. Thevoltage with reference toground which appears at theleft-hand, end. of inductance winding 139. is icon nested throughconductors 38 and 53,.and resistor li.9,.,to {the ,gricltof therightehand .triode of tube d6, Thus the grid of the right-hand triode oftube 4.5: is controlled in accordance with :the potentialsdeveloped-across the oscillatory circuit and the plate circuit ,of, theright-hand triode becomes conductive whenever the voltage .appliedto'the grid becomes...m0re. positive thanv that of the cathode,and.becomes.)non-conducting -Whenever the yoltage applieditothe grid.becomes--more negatiVe-Tthanthe cathode. Each time the anode circuit ofz the, right-hand. triode passes from -theconductive. to thenon-conductive condition-a positive. impulse-is applied to thesecondaryof tliansformerl 66. The -.potentiornetersBil-and; B3fromawhich. the cathode and: anode potentials fortharight-hand triode of'tube d6--are derived provide for varyingithe cathode potential withrespect tot-ground without changing theplatetoecathode potential. Thisprovides for--orientation.of,.-the positivev pulses-generated inthe-secondary of transformer 66 withrespect-to the oscillatory'cyclesgeneratedby the dischargetube oscillator, by which is meant that thetime of, occurrence of the positive impulse in-thes econ" dar y oftransformer. 65 relative to each cycle .of oscillation of the oscillatormay be varied.

The terminal of the secondary of .transformer 66 which is negative whenthe righthand triode oi tube lfi passesfrom conductive to non-:conduc-i.tive condition, is connected through tconductor It. resistor is andresistor Zdtothe positive terminal of battery 26.x and throughzresistor.lh to ground. The other terminal of the secondary. of transformerfifiis. connected-by conductor :14;-

to branching circuits through resistors'lfi and Tie to the controlanodes .of cold cathode gas-filled; dischargetubes ll '1 ,and; I8,respectively.

relay-.1 9 to ground; In the case'of tube l1;,': with tl-" e armature ofrelay H. onthe marking contact a reverse voltagelis applied fromthe-negative terminal-bf battery/$13.! throughresistors 29" and 25-,-.-conductor.- 28,: armature :and marking contact of relay; t!resistord 4; controllanodeiand cathode ofatube H andi-right-hand windingof relayr'l9 to ground, which iszatthe potential of thet-positi-ve;terminal;ofrbatterysai; =The voltage across the control :gapofa-tu-be l1-is thus seen to be the difference; between the; voltages.supplied by bat teriesl-fi and SI, and; this difference may be 'zero sothat thereis nopotential across the control apof tube l1;,-or-battery 26maybevof slightly higher voltage than battery-it'll; so :as to'supply apositive potential difference of the control anode with respect to thecathode of-a=few volts,ipro'+ vided such potential. difference is wellbelowuthe firing potential ofthe control gap; Since with the armature ofrelay engaging the marking contact battery 3| is. disconnected from thecontrol anode oftube l8, .the potential of batteryrzfi reduced by the.voltage :divider. comprisingE resistors-l3andll is; applied across thecontrol gap of tube 18, with the. positivepotential applied :to

the-control anode butnthis potential shouldrbe well below the: firingpotential of the control: gap of the tube andmay; for example, be oftheorder of fiftygvoltsu-"onei-ora-the other ofthe tubes'il-l and :l 8.,mustbeconducting, Ia's-will be described later, and... since -thearmature of relay "1 l J is shown in, engagement with. the markingcontact for the idle: pondition of the apparatus .it :will

be. assumed that: tube l8'iwhich' controls the transmission ofr-markingimpulses is conducting: It'uiS tQJ-beHHOtBd thatthe control anodeor thistube is connected to the spacing. contact of 're-- ceiving relay andthe. reason mentwillappear later.. 7

With further and more detailed reference to the circuitbf batteries 26and 3|, the resistor H "is common to their returnpaths to ground. Sincefor this arrangethese batteries are oppositely connected with-re spectto. resistorJL-they seek to drive current therethroughinopposite-directions. The polarity ofmtheipotential. difi'erence acrossthe resistor M will depend, upon therelativevoltages of batteries ZSand3| andtheresistivepotential differences in their individualcircuitswhich join at the resistor,

H.- -Witl'1 the armature of receiving relay H on its marking 'contactthe potential across the control gap "of the'inactive tube I! will beless positive thanthepotential"difierence across the resistor 'H by thepotential difference across resistorv 16 due to current flowing frombattery 3l..;...The potential difference across the control gap of :tubeI8: will besubstantially equal to' the potential difference acrossresistor H because there; is no current flowing in resistor'l'l exceptfor thepossibility of a very small current flowing from the controlanode 0f tube 8 which is conductive atathis'time. The values of theresistors are such' that the potential difference across resistor I6 isonly a few volts less than the potential difference across resistor I Iand being opposite in polarity it impresses on the control anode of tubeI I a positive potential of a few volts with respect to the groundedcathode. The potential of the control anode of tube I8 with respect tothe cathode is at a value intermediate that on the control gap of tubeI1 and the firing potential of these tubes. This potential may be of theorder of 50 volts as previously set forth.

Upon the movement of the armature of relay II into engagement with thespacing contact in response to the start signal, battery 3| isdisconnected from the control anode of tube I1 and becomes connected tothe control anode of tube I8. Thus the voltage of battery 26 reduced bythe potentiometer comprising resistors I3 and II is applied across thecontrol gap of tube I1 and this voltage opposed and reduced by thevoltage across resistor 11 produced by current from battery 3| isapplied across the control gap of tube I8. These conditions do not ofthemselves change the operative condition of tubes I1 and I8 because thevoltage applied across the control gap of tube II, assumed to be of theorder of fifty volts, is insufiicient to fire that control gap and thereduction in voltage across the control gap of tube I8 to a few volts orto zero cannot deactivate the tube. The first cycle of oscillatorycurrent generated by the oscillator as a result of reception of thestart signal results in the production of a voltage across the secondaryof transformer 66 at a timed instant just before or just after themiddle of the cycle of oscillatory current as determined bypotentiometers 59 and 63. The voltage developed across the secondary oftransformer 66 aids the potential difference across the control gap oftube I1 applied by battery 26, as may be observed by tracing the circuitfrom the positive terminal of battery 26, through resistors 24 and I3,conductor I2, winding of the secondary of transformer 66 from negativeto positive end, conductor 14, resistor I6, control anode and cathode oftube I1 and right-hand winding of relay IE! to ground. The aidingvoltage in the secondary of transformer 66 is also applied throughresistor I1 and across the control gap of tube I8 through the left-handwinding of relay I9 to ground but the voltage of battery 26 aided by thevoltage in the secondary of transformer 66 and opposed by the voltage ofbattery 3| is below the firing potential of tube I8. This is of noimmediate consequence as tube I8 has been assumed to be conductive atthis time. The voltage supplied by battery 26, assumed to be of theorder of fifty volts, aided by the voltage of transformer 66, which willalso be assumed to be of the order of fifty volts, produces a, potentialdifference across the control gap of tube 11 of the order of one hundredvolts which is suificient to fire the control gap and, accordingly, themain gap between the main anode and the cathode of tube I! becomesconductive and the right-hand winding of relay I9 is energized. Thefiring of the main gap of tube I'I results in the production of animpulse through condenser 21 to the main anode of tube I8 which reducesthe potential of the anode relative to the cathode below the dischargesustaining potential. Accordingly, the main gap of tube I8 from mainanode to cathode is rendered nonconductive and the left-hand winding ofrelay I9 is deenergized. The right-hand winding therefore assumescontrol of the armature and moves the armature to the spacing contact,thus impressing a spacing impulse on transmitting line 2|.

Assuming that the voltage developed across the secondary of transformer66 should persist after the main gap of tube I8 has been quenched, thecontrol gap will not be fired, due to the fact that the voltage acrossthis gap resulting from the battery 26 aided by the voltage in thesecondary of transformer 66 but opposed by the voltage of battery 3| isbelow the control gap firing potential. It is to avoid the undesiredrefiring of tube I8 that the voltage developed across the secondary oftransformer 66 should be suflicient to fire the control gap of the tubeI1 or tube I8 with the aid of battery 26 only when unopposed by thebattery 3| but should not be sufiicient to accomplish this when opposedby the battery 3|.

When the armature of relay II' is again restored to marking in responseto a marking signal in the received code combination the opposing effectof battery 3| will be removed from tube I8 and will be applied to tubeH. The firing of tube I8 will await the production of the impulse of theproper polarity in the secondary of transformer 66 under the control ofthe oscillator, and when the impulse is generated the control gap andthen the main gap of tube I8 will be fired and the main gap of tube IIwill be quenched, whereupon the left-hand winding of relay I9 will movethe armature to the marking contact. From the foregoing it will beapparent that relay I9 is operated by the commutating tubes I1 and I8under the control of relay I I as to marking and spacing conditions andat timed intervals as determined by the oscillator. Thus the oscillatordetermines the several instants at which relay I9 shall move itsarmature from one contact to the other and si naling impulses receivedin weak or distorted condition will be retransmitted as full length andfull strength impulses. The orientation feature afforded by thepotentiometers 59 and 63 enables the right-hand triode of tube 46 toeffect the operation of tube IT or tube I8 when the most efiective partof each signaling impulse is be ing received by the relay I'I so thatthe armature of the receiving relay will have arrived at its properselective position when the impulse for firing one ,of the commutatingtubes I1 and I8 is generated. When two successive impulses in a codecombination are alike, the armature of relay I I is in the same positionwhen the positive impulse is generated in the secondary of transformer66 for each of the two signaling impulses, so that the control gap ofthe same one of the tubes I! or I8 is refired in response to the secondimpulse. Since the main gap of the refired tube is already conducting,the refiring oi the control gap has no effect.

At the same time that the grid of the righthand triode section of tube46 is made positive with respect to ground through the resistor 69 underthe control of the oscillatory circuit the grid of the right-hand triodesection of a tube BI is made positive with respect to its groundedcathode under the same control through a resistor 82. The anode of theright-hand triode section of tube BI is connected through the primary oftransformer 83, which is shunted by resistor 84, and through resistor 86to the positive terminal of grounded battery 81. The right-hand triodeof tube 8I is thus rendered conductive once for each cycle of theoscillator and when current rises in its anode circuit an impulse isgenerated in the secondary or transformer 83, one terminal of which isconnected through resistor 29 to the negative terminal :of groundedbattery 3| andthe other terminal of which is connected to the grid andanodeof the right-hand triode section of tube 8| which, having'its gridand an ode connected together. operates as a diode. The impulsegenerated in the secondary of transformer 83 as current rises in theanode section of the right-handtriode is positive toward the anode andgrid of the left-hand triode section and negative toward the battery 3|.The voltage developed across the secondary of transformer 83 issufiicient to overcome the negative voltage applied in! battery 3| sothat the interconnected anode and grid are made sufiiciently positivefor the tube to be conductive. The voltage of opposite polaritygenerated in'thesecondary of transformer 83 when the grid of theright-hand triode section of tube 8| is restored to negative withrespect to the cathode .and current is cut off in the right-hand triodesection, has no effect on the diode-connected left-hand section of tube8| since that section .is conductive .in only one direction.

The cathode of the left-hand section of tube 8| is connected through avariable resistor 88 to the grid of the right-hand triode section of atwin triode electron discharge tube 89 and is also connected to :onesideof acondenser 9| the other side of which is connected to the anode .ofthe lefthand triode section -of tube 89. Each time that the left-handsection of tube 8| is conductive the flow of cathode current causes acharge to be impressed upon condenser 9| which is positive on 1:

the side of the condenser connected to the grid of the right-hand triodesection of tube 89. The circuit is so adjusted that when a fullpermutation code signal has been received which, in the case of a codehaving five selecting impulses is sometimes called a seven-unit code ifthe start and stop impulses are each of one unit impulse length, or'aseven and one-half unit code in case the start .impulse is of one code:impulse'un'it length and the stop .pulse is-substantially one andone-half code impulse unit length, the condenser 9! will have receivedseven charging impulses under thecontrol of thexseven cycles ofoscillatory current generated by the zosci'llatorzand the sevenaccumulated impulses raise the potential of the grid sufiiciently withrespect to the grounded cathode to render the right-hand section of tube89 conductive. The anode of "the right-hand section of tube .89 .isconnected through resistor '92, conductors 93 and 9 -1 and resistor 88to the positive terminal of grounded battery 81. The anode of theright-hand :section of tube 89 is also connected to one side of acondenser 96 the other side of which is connected to the grid of thelefthand triode section of tube 89 and is also connected throughresistor "9'! to ground. 'Dueto the flow of anode current in theright-hand section of tube 89 the potential-ofthe anodebecomes lesspositive, which causes condenser 98 to discharge thus producing aflow-of currentthrough "resistor '91 and driving the grid "oft-heleft-hand section of tube 89 more negative than the ground potentialwhich it had when no current was flowing through resistor 9'8. Theleft-hand triodesection of tube 89 is normally conductive and when thepotential of the grid is made negative with respect to the groundedcathode, current 'in the left-hand triode section is cut off. The anodeof the lefthand section of tube 89 is connected through 99 to conductor94 and thus to the positive terminal of battery 81. The right-hand endof the secondary winding of transformer '99 is connected to the controlanode of discharge tube 3 1 and the left-hand end of the secondarywinding is connected to the cathode of that tube. The impulse generatedin the secondary of transformer 99 when current in the'left-hand sectionof tube 89 is out off is positive toward the control anodeof dischargetube 34 and negative toward the oathode and is of suiiicient voltage tofire the control gap of tube 34. If receiving relay H is at this time inmarking position which it should be in response to the stop impulse,battery 3| is connected to the cathode of tube 34 so that the main gapof the tube will be fired. Since at this time the oscillatorhas producedseven complete cycles, and since its decrement is substantially zero,current and voltage conditions in the oscillatory circuit have returnedto their initial values. The firing of tube '34 theretore merely holdsthe oscillator and no stoppingtransient results. If, however, thedecrement is other than zero, the final amplitude will difier from theinitial amplitude. To take care of this condition, the values ofresistances and 33 are so chosen that the circuit returns to its initialcondition in critically damped manner and the stopping transient is ofthe shortest possible duration. Thus the production of timing impulsesis suspended and the system awaits the reception .of the next startimpulse.

When theanode current was cut off in the lefthand section of tube @89the anode potential was made more positive which. through condenser 91makes 'thegrid of theright-hand triode section of tube 8.9 morepositive. Not only does the righthand triode section of tube 89 continueto be conductive after anode current in the left-hand section has beencut off, but due to the positive potential of the grid it draws currentthus charging condenser 91.. After .a short while .condenser 98 changesthrough resistor .911 thus bringing the grid of the left-hand section oftube 89 .to ground potential .and reactivating the left-hand section ofthe tube. With the restoration .of anode current :in the left-handsection of tube 89 the anode potential of that section is made lesspositive by virtue of the .fiow :of current in resistor 19.8 :andthrough condenser 9.! the grid of the right-hand triodesection is drivento negative potential with respect to the grounded cathode :thus cutting.off anode .current in the right-hand section of the tube and restoringthe system to normal.

Had the received signal combination been so distorted that the stopsignal was not .being received at the time the voltage developed acrossthe secondary ro-f transformer .99 fired the control gap of tube M. themain gap of tube 3.4 would not have been fired because of the absence ofnegative battery connection for the cathode of tube 3'4 at the markingcontact of relay M since presumably the armature of relay might not havereturned tomarlrin position. Under these circumstances the oscillatorwould not be stopped but would continue to produce timing cycles ofoscillatory current irom'which impulses would be derived for chargingcondenser 9| and when seven cycles of oscillatory current had beengenerated the right-hand triode of tube 88 would again be activated andthe control .gap of tube .34 would again be .fired seeking toreestablish the main gap discharge in the tube 3 4 under the control ofthe armature of receiving relay I I. It should resistor 98 and primarywinding "of transformer be'inoted that when the left-hand triode sectionof tube 89 is restored to conductive condition under the control of theright-hand triode section, an impulse is generated in the secondary oftransformer 39 of the opposite polarity to that which refired thecontrol gap of tube 34. Since the main gap or the tube has already beenrendered conductive, the application of the reverse voltage across thecontrol gap will have no effect.

In the embodiment of the invention shown in Fig. 2, the receiving relayIOI has its operating winding connected to the receiving line I02 and,in the idle condition, the operating winding is energized and holds thearmature on the marking contact. The biasing winding of relay IOI hasbattery connection of the proper polarity to operate the armature tospacing when the line I02 is interrupted at the transmitting station.The marking contact of relay IOI is connected through resistors I03,I04, I06, I01 and inductance I08 all in series to the anode of a hotcathode, gasfilled, grid controlled, electron discharge tube I09. Thearmature of relay IIiI is connected to ground and the cathode of tubeI09 is connected through resistor III to the negative terminal ofbattery II2, the positive terminal of which is grounded.

Thus the resistors I03, I04, I06, I01 and III and the inductance I08 areincluded in the anodecathode current path of tube I09.

Cathode resistor III of tube I09 is shunted by a condenser I I3 which ischarged to the potential diiierence across the cathode resistor whentube I09 is conductive, which is the normal idle condition. A potentialdivider comprising resistors H6 and II1 is connected between thenegative terminal of battery H2 and ground and the grid of tube I isconnected through grid current limiting resistor H8 to the junction ofresistors H6 and I II. The grid of tube I09 is at all times morepositive than the negative terminal of battery II2 by the potentialdifference across resistor H0, but the cathode of tube I09 is morepositive than the negative terminal of battery I I2 by the potentialdifference across resistor III when tube I09 is conductive and theresistors are of such relative values that the grid of tube I09 is lesspositive than the cathode by an amount at least equal to the cut-offvalue of the tube, so that the grid would render the tube non-conductiveexcept for the fact that the tube is gasfilled and the conductivity ofthe tube-is not responsive to the negative potential of the grid oncethe tube has been rendered conductive. The condenser H3 in combinationwith the cathode resistor ii I serves to perform a character timingoperation as will be described later.

The resistor I01 and inductance I08 connected in series are shunted by acondenser I2I and the junction at of the resistor and inductance isconnected through grid current limiting resistor I22 to the grid of ahot cathode, gas-filled, grid controlled, electron discharge tube I23.The network comprising resistor I01, inductance I08 and condenser I2I isan oscillatory circuit for controlling the conductivity of tube I23.Power for operating tube I23 is supplied from alternating current powerline conductors I24 through primary and center tapped secondary windingsof transformer I26, full wave rectifier tube I21, smoothing filtercomprising condensers I28 and I and choke oil ISI, and output potentialdivider comprising resistors I32 and I33 in series.

The anode of tube I23 is connected through load resistor I34 to theupper end of resistor I32 which is the positive terminal of the powersupply of tubes MI and I42.

and the cathode of tube I23 is connected to an adjustable contactorassociated with resistor I33. The primary windin of a transformer I36 isconnected in series with a condenser I31 between the anode and cathodeof tube I23. Instead of the power supply comprising an alternatingcurrent rectifier and smoothing filter, a battery could be employed forsupplying operating power for tube I23. It will be noted that neitherthe positive nor the negative terminal of the power supply is grounded.The reason for this is that a floating source of potential is requiredfor tube I23 as will be more fully described later and if a batteryshould be substituted for the power supply, it cannot be the battery H2or any other battery supplying power to other parts of the circuit butmust be a separate battery in order that neither of its terminals shallbe grounded.

Resistors I04 and I06 in series are shunted by a condenser I38 and thisnetwork comprises an aperiodic circuit with condenser I38 charged to thepotential across resistors I04 and I06 in series when tube I09 isconductive. The junction 0 of resistors I 04 and I06 is connected to thenegative terminal of the power supply for tube I23 and this connectionis the cathode return for the grid of tube I23. With tube I09 conductivethe grid of tube I23 is negative with respect to the cathode by thepotential difierence across the resistors I01 and I06 plus the potentialdifference across that portion of resistor I23 between its lower end andthe cathode contactor, this latter potential difierence being in thesame polar sense or direction as the potential difference acrossresistors I01 and I06 and therefore being added to the potentialdifierence across resistors I01 and I06. The grid of tube I23 is biasedby the sum of these potential differences to a sufficiently negativevalue to hold tube I23 non-conductive and in the idle condition the tubeis non-conductive.

The signal repeating circuit is associated with the marking and spacingcontacts of receiving relay IOI. It includes a pair of hot cathode,gasfilled, grid controlled electron discharge tubes MI and I42 in acommutating circuit. The marking contact is connected through resistorsI43 and I44 to the grid of tube I42 and the spacing contact is connectedthrough resistors I46 and I41 to the grid of tube I4I. Negativepotential is supplied from battery I48, the positive terminal of whichis grounded, through resistor I49 to the junction of resistors I46 andI41 and through resistor I5I to the junction of resistors I43 and I44.The cathodes of tubes MI and I42 are connected through the secondarywinding of transformer I36 to ground. The anodes of tubes MI and I42 areconnected through the oppositely poled windings of a polar sending relayI52 to the positive terminal of battery I53, the negative terminal ofwhich is grounded.

The armature and marking contact of relay I53 are connected to the twoconductors of an outgoing telegraph line I54. A tube quenching condenserI56 is connected between the anodes In the idle condition tube I 42 isconductive and current flowing in the lower winding of relay I52operates the armature of the relay to the marking contact. Tube I M isnon-conductive.

Assume that the normal idle condition exists with tubes I09 and I42conductive and tubes I23 and MI non-conductive, and that the startimpulse of a permutation code combination is received. As the armatureof receiving relay IOI leaves the marking contact it interrupts theanode circuit of tube 109 thus cutting off "current "in the tube andthis tube 'deioniz'es. Due to the charge on condenser lls, the potentialdilrerence across cathode resistor l H, which is or relatively highresistive value, decreases slowly as condenser H3 discharges throughresistor HI, and the potential of the cathode will not "belcrrcug-htdown to a value at which grid of tube' l 09 can'refire the tube untilabout the time that the stop impulse at "the end of the code combinationf'sh'ould be received. In this way condenser H3 and resistor "I II timethe rei'irin'g of tube 1'09 to '-''a character interval.

Another result "of the departure of the armature of receiving relay l '0from the marking 'contact is that a circuit from battery M8 throughresistors IEI and I 13 to ground is interrupted, terminating the flow ofcur-rent through resistor fl'r l and making the grid of tube I42 morenegative with respect to the cathode than it pre- "vi'ously was by the aindl-ln t 0f the potential difrerence which previously existed'a'ci'o's's resistor "I51 This change in the potential *of the grid orto e M2 will not cause tub 142 to be cut on because the tube isgas-filled and grid can not perform this operation.

Upon arrival of the armature of receiving re- :lay IB'I at the spacingcontact, a circuit is established from battery '8 through resistors M9and M6, the armature and spacing contact of relay 1 91 to ground. Thejunctionof'resistors Hi9 and 1 46 is made less negative than itpreviously was by the amount of potential icli'ffere'nce across re.-'sistor I49 resulting iro'm the flow of current established in the"circuit just traced. "l he cathode of tube M l is substantially atground potential due to its connection to ground through the secondary0f transformer I36. Even with current flowing in resistor I49, thegrid'of tube I'M is not thereby brought to such potential that it canIrender tube Ml conductive.

With the How of anode current :of tube Hi9 through resistors +834, 166and PM and the in- :ductance I'l'IS interrupted, the network comprisingresistor 1 01, inductance I08 and condenser I21 breaks into oscillation.The values of :induotance I98 and condenser IQ'I are such that thecircuit oscillates at the rate of one cycle zper impulse interval ofcorrectly timed per-mu-' tation code signals, which is sometimesreferred to as a-f-requency twice that of the signaling frequency,considering a marking and a spacing pulse each of a duration of oneimpulse interval as a signaling cycle. Due to the fact that there is noprovision for feeding energy back into the oscillatory circuit tocompensate for resistive energy losses within the circuit, theoscillator circuit will oscillate decrementally .by which is meant thatthe amplitude of oscillation decreases throughout successive halfcycles. tube I23 is connected to the right hand end of resistor I Ill,which is the junction at and the voltage across this resistor, startingat a negative maximum at its right hand end performs a dampedoscillation, as shown in Fig. 4, alternatel rising above and fallingbelow the :potential at the junction b of resistors 3'6 and I'll! asare'felencepoin't. I

At the same time that the oscillator circuit breaks into oscillation,condenser "[38 begins to discharge through resistors I04 and .I'll'fi.The potential difierence across resistor N16 is amaximum just beforecondenser I38 begins to dischargalw-ith the junction b of resistors I416and Ill! negative with respect to the dunction c of re? The grid of tothat fof the cathode only sisters 'MPand I 06, and this potentialdifibrence uecreaseswith thel'ighthand end resistor 1116 becominglessnegative-with respect to the lunction 0 of resistors I 0-4 and 1 06which is connected to the cathode ofth e tube $23 through 'a portion'ofresist'o'r 133. The constants *of the aperiodic network comprisingresistors I04 and I06 and condenser I 38 are so chosen that the curverepreseating the potential of the right hand end of resistor Hit Withrespect to the 'lellt'hand end as time relapses, shown in Fig. 5,coincides with'the envelope or the oscillatory current across resistor:I-IFI which envelope-is the curve of the decreasing amplitudes ofsuccessive cycles of the oscillatory potential across resistor ill-1During the half cycle of oscillation 'in which the right hand end ofresistor l'ol is positive with respect to the-left hand end, thepotential difference across resistor m! :is op osed by-the potentialdiffert-ince across res'isto'r ms and during the remaining half cyclesthe potential difference across resistor 1 0B in series aiding relationto the potential difference across :r esistor 107-. The algebraic sumfOf these potentials imoressedbetween the grid and the cathode of tube I28. Considering the 'junct ionc as a "zero reference point, the resultor the alga brai'c addition ofth'e oscillatory potential in theoscillatory 'c'irtiltiit and of the decaying potential in the aperiodiccircuit is to shift upwardly "the zero axis relative to potentialsapplied to the grid of the tube. By prop'ontioning the two "circuits sothat the initial amplitude of the potent l'a'cross resistor 106 in theaperiodic circuit is equal to the initial amplitude of the potentialacross resistor It ins-the oscillatory circuit, and *so that the timeconstant'of the discharge or the condenser in the aperiodic circuit isidentical with the time constant of the envelope of the oscillatory-'current, the .peak voltages in the po'sitive half cycles ofoscillatory operation are brought into coincidence with the shiftedzei'o axis as -'shown in Fig. 6 which is the zero reference potential ofjunction 0. Fromlthi's it follows that the potential of the grid risesto a value that is negative with res ect by the potential dif- 'ferenceacross that ortion "of the resistor I '33 between the lower and themovable contactor once in each :cycle of the oscillatory circuit and atall other times is more negative with respect to the cathode.

When the :grid of tube I 2 3'reaches a predetermined potential near thatof the cathode, tube 423 is rendered conductive. The tube, upon firing,completes an -=oscillatory circuit through -the primary of transformerl36 and condenser I37. The current in this circuit rises-to a peak andthen falls to zero tending to reverse. The current results from thedischarging "of condenser I31 and induces potentia-ls in the primary oftransformer L36. When the sum 'of the potentials across the transformerprimary and the condenser becomes less than the discharge sustainingpotential, the discharge in "the tube is quenched and in the meantimethe grid of the tube has been carried sufficientl negative with respectto the cathode by the oscillatory circuit that the tube is preventedf-r'om refir'lng and deionizes and remains non-conductive until the gridapproaches cathode "potential in the next cycle of the oscillator.

The rise and fall of current in "the primary winding of transform-er I36generates an impulse :in the secondary which is connected between groundand the cathodes of tubes 1-241 and 15 At one phase in the generation ofpotentials in the secondary of transformer I36 the potential generatedis positive toward ground and negative towards the cathode of tubes MIand I42. This reduces the potential of the cathodes with respect totheir grids. With the armature of receiving relay IBI engaging thespacing contact in response to the start impulse, the grid of tube MI isless negative than the grid of tube I42 as previously described. Thecathode of tube I4I= is brought toward negative by the impulse generatedin the secondary of transformer I36 to an extent with respect to thegrid that permits tube I4I to become conductive. The discharge currentflows in the upper winding of relay I52 and at the same time a negativepulse is impressed through condenser I56 on the anode of tube I42reducing the anode-cathode potential in that tube below the dischargesustaining potential and quenching the tube. At the time tube I42 isquenched, the grid of the tube is more negative with respect to thecathode than is the grid of tube I4I even though the cathodes may atthat instant be at the reduced potential resulting from the generationof the impulse of the secondary of transformer I36 so that the grid willnot cause tube I42 to be refired and the tube will deionize. Withcurrent interrupted in the lower winding of relay I52, and flowing inthe upper winding, the

armature of the relay will be operated to spacing,

opening the outgoing telegraph line and retransmitting the start impulseof spacing nature.

In the next cycle of the oscillatory circuit when tube I23 is renderedconductive momentarily, another impulse will be generated in thesecondary of transformer I36 momentarily reducing or rendering lesspositive the potential of the cathodes of tubes MI and I42. If thearmature of relay IN is then on the spacing contact indicative of thefact that the first significant impulse of the code combination to berepeated is spacing, tube I42 will not be rendered conductive becausethe potential of the cathode will not be lowered sufiiciently toovercome the negative bias on the grid and tube I4I will remainconductive without interruption, the armature of transmitting relay I52remaining on the spacing contact. If, however, the first significantimpulse of the code combination is marking and the armature of relay I Mhas returned to the marking contact, tube I42 will be conditioned to befired by the armature of the receiving relay I Ill and will be firedwhen the pulse of the proper polarity is generated in the secondary oftransformer I36 and tube I42 in firing will quench tube I4I therebyoperating transmitting relay I52 to restore the armature to the markingcontact.

Fig. 3 represents a received signal that is to be regenerated andretransmitted. The shaded areas represent possible conditions ofdistortion. Specifically, the first shaded area represents the conditionof marking bias, the second shaded area represents the condition ofmarking end distortion and the third shaded area represents thecondition of spacing bias. As indicated by Figs. 4 and 6, the junction aand therefore the grid of tube I23 reaches its most positive potential,and therefore its minimum negative potential with respect to junction 0and the cathode of tube I 23 one-half impulse interval after receptionof the beginning of the start impulse and at successive impulseintervals thereafter since bias and end distortion advance or retardvarious transitions relative to the beginning of the start ,I06, I01,III and inductance I08.

current stops the flow of oscillatory current in impulse, they do notaffect the middle portions of signals unless the signals have become somultilated as to be unintelligible. Accordingly, by causing tube I23 tofire at the middle of the received start impulse and at unit impulseintervals thereafter, the armature of receiving relay i0! is mostcertain to have reached a steady condition representing the impulse tobe repeated. Since the firing of tube I23 determines the beginning ofeach retransmitted impulse, the retransmitted signal is delayed one-halfimpulse interval with respect to the received signal, and the startimpulse and each selective impulse is of full duration, as representedin Fig. 7.

As the successive significant impulses of a telegraph code combinationare received, the tubes I4I and 542 are alternatively conditioned to befired in accordance with the spacing or marking nature of the impulsesreceived by receiving relay RBI and the tube I23 controlled by theoscillatory circuit times the firing of these tubes. In this way thelength of each retransmitted impulse is determined by the oscillatorycircuit and a full impulse interval is allotted to each impulse, whichconstitutes regeneration of the signal and elimination of distortion.

About the time of the seventh activation of tube I23, for five unit codepermutation code signals comprising a start impulse, five significantimpulses and a stop impulse, or of the eighth activation of tube I23,for six unit code permutation code signals comprising a start impulse,six significant code impulses and a stop impulse, condenser II3 hasbecome discharged and reduced the positive potential of the cathode oftube I09 relative to the grid to the firing potential of the tube. Atthis time the receiving relay IOI should be responding to the stopimpulse of marking nature and the armature of the relay should be on themarking contact. Also, the seventh activation of tube I23 should haveoccurred and should have activated tube I42 for the retransmission ofthe stop impulse. Upon being reactivated the tube I09 causes a flow ofsteady current through resistors I03, I04, This steady the oscillatorycircuit and reestablishes a steady current condition in inductance I08associated with that network. It also recharges condenser I33 to theprevious initial value. Resistors I03 and II I which are in series withbut are outside the oscillatory and aperiodic networks have such valuesthat the oscillatory network and the aperiodic network return to theinitial steady state condition in the shortest possible time. Theapparatus will remain in this condition until the start impulse of thenext code combination is received.

It was previously mentioned that the power supply for tube I23 is anungrounded and therefore floating power supply. This is necessarybecause in response to each marking signal, the grounded armature ofreceiving relay IOI engages the marking contact which is connected tothe negative side of the power supply through resistor I03 and resistorI04 of the aperiodic network. If any part of the output of the powersupply for tube I23 should be held at ground potential, current might becaused to flow from the power supply through resistor 504 and resistorI03, or the resistor I04 might be shortcircuited in the case of thedirect grounding of the negative side of the power supply, which woulddisturb the operation of the aperiodic cir- In the description of theoperation of the oscillatory network and they aperiodic network tocontrol tube I 23', reference wasmade to the effect of that portion ofpotential divider I 331 between the contactor and] the lower or negativeend of the resistance winding, namely, to provide a minimum negativebias onthe grid of tube I23. The zero axis in Fig. 6 represents thepotential of the cathodefbut the potential at" the junction 0. If thecontactor should be. moved down to the lower end of potential, dividerI33; the cathode wouldhave the same potential as the point e. Thecathode is more positive than the point by an adjustable amountdetermined by the position of the contactor with respect to the windingof potential divider resistor I33. The potential divider I33pprovidesfor a certain amount of orientation adjustment, taking advantage of thecharacteristics of grid controlled gas-filled electron discharge tubesthat the tube will be rendered cond'uctivewhen the grid, approaching thepotential of the cathode, reaches. a predetermined negative, voltagewith respect to the cathode. It. is not 'necessaryior the grid to reachthe potential ofthe cathode or to be: come positive with respect theretoin. order to establish conductivity. For any setting, ofv the contactorof the potential divider resistor I33, when the potential of the grid oftube I23, ris.-,

ing to less. negative values, reaches that negative value relative tothe cathodewhich is the characteristic conductivity potential differenceof grid to cathode, the tube will be rendered conductive. The earliestpossible firing.of.the tube relative to the cycles of oscillatorycurrent will occur when the. contactor of potential divider I33 is moveddownto thelower end of the resistance winding because this representscomplete removal of the fixed biason the. tube. The. latest possibleinstant of firing, of tube I23 relative to the cycles of oscillatorycurrent. coincides. with.

the most positive peaksof the oscillatory potentials applied to the-gridbecause this represents the condition of minimum potential difierencebetween the cathode andgrid and-firing of the tube at this instant willoccur when the fixed bias is so adjustedby means of potential divider I33 that the grid just reaches the minimum negative potential relative tothe cathode for firing the tube. If the fixed bias should be in: creasedby movingthe contactor of potential divider I33 still farther from thelower end of the resistancewinding, tube I23- will not be activatedcyclically under the control of the oscillatory network and signals willnot be transmitted.

With the potential of the junction 11 arranged to start from extremenegative potential with respect to junction b, to rise to extremepositive value, and return to maximum negative, in an interval equal toone telegraph impulse interval and under the control of a received startimpulse, the peak positive voltage of junction a will occur 1'8 one-halfimpulse interval after the departure. of the'armature of receiving relayIOI away from the marking contact in response to the start impulse andsubsequent peak voltage conditions will occur at successive impulseintervals thereafter. From this it follows that the beginning ofretransmission of the start impulse may be delayed a maximum of one-halfof a telegraph impulseinterval after the start impulse-is eifective uponreceiving relay Ill-I as shown in Fig. 7, and that the retransmission ofthe start impulse may be initiated earlier than one-half of a telegraph;impulse interval after the receiving relay responds to the start impulseby means of the orientation adjustment described in the precedingparagraph. The initiation of all subsequent impulses within a codecombination will occur at unit-intervals after the initiation of retransmission of the start impulse.

What is claimed is:

1. In a telegraphsignal repeater, a signal responsive relay, a normallyinactive impulse generator, normally conductive electron dischargemeansrenderednon-conductive by said signal responsive relay uponresponse thereof to a signal for activating said impulse generator, asignal transmitting relay, means controlled jointly by said'signalresponsive relay and said impulse generator for controlling saidtransmitting relay, and means for reactivating said electron dischargemeans a predetermined interval after the deactivation thereof whereby todisable said impulse generator.

2. In a telegraph signal repeater, a signal responsive relay a normallyinactive impulse generator, a normally conductive gas-filled electrondischarge tube rendered non-conductive by said signal responsive relayupon reponse thereof 'to a signal for activatingsaid impulse generator,a

signal transmitting relay, means controlled jointlyby said signalresponsive relay and said impulse generator for controlling saidtransmitting relay, and means for reactivating said gas-filled tube apredetermined interval after the deactivation thereof whereby to disablesaid impulse generator.

3. In a telegraph signal repeater, a signal responsive relay, a normallyconductive gas-filled electron discharge tube having its anode circuitnormally completed through the armature and marking contact of saidrelay and adapted to be deactivated upon response of saidrelay to asignal, a normally inactive impulse generator adapted to be activated bysaidelectron discharge tube upon the deactivation thereof, a signaltransmitting relay, means controlled jointly by said signal responsiverelay and said impulse generator for' controlling said transmittingrelay, andmeans for reactivating said gas-filled electron discharge tubea predetermined interval after the deactivation thereof whereby todisable saidimpulse generator 4. In a telegraph signal repeater, asignal responsive relay, a signal transmittin relay, and an impulsegenerator for controlling said transmitting' relay' jointly with saidsignal responsive relay, said impulse generator comprising an0scillatory circuit adapted to generate an oscillatory potential havingdecremental amplitude, an electron discharge tube having an anode, acathode and a control electrode and having its control electrodeconnected to said oscillatory circuit, and means connected between saidoscillatory circuit and said cathode for causing said control electrodeto reach a predetermined potential with respect to said cathode at theamplitude extremes of alternate half cycles of said oscillatorypotential.

5. In a telegraph signal repeater, a signal responsive relay, a signaltransmitting relay, and an impulse generator for controlling saidtransmitting relay jointly with said signal responsive relay, saidimpulse generator comprising an oscillatory circuit adapted to generatean oscillatory potential having decremental amplitude, an electrondischarge tube having an anode, a cathode and a control electrode, andhaving its control electrode connected to said oscillatory circuit, anda resistor and condenser network connected between said oscillatorycircuit and said cathode having a potential difference timecharacteristic substantially identical with the envelope of saidoscillatory potential for causing said control electrode to reach apredetermined potential with respect to said cathode at the amplitudeextremes of alternate half cycles of said oscillatory potential.

6. In a telegraph signal repeater, a signal responsive relay, a signaltransmitting relay, and an impulse generator for controlling saidtransmitting relay jointly with said signal responsive relay, saidimpulse generator comprising an oscillatory circuit adapted to generatean oscillatory potential having decremental amplitude, an electrondischarge tube havin an anode, a cathode and a control electrode andhaving its control electrode connected to said oscillatory circuit, anda resistor and condenser network connected between said oscillatorycircuit and said cathode having a potential difference timecharacteristic substantially identical in configuration and magnitudewith the envelope of said oscillatory potential for causing said controlelectrode to reach a predetermined potential with respect to saidcathode at the amplitude extremes of alternate half cycles of saidoscillatory potential.

7. In a telegraph signal repeater, a signal responsive relay, a normallyactivated electron discharge tube adapted to be deactivated by saidsignal responsive relay upon response thereof to a signal, a signaltransmitting relay, a normally inactive impulse generator renderedactive by said electron discharge tube upon the deactivation of saidtube for controlling said transmitting relay jointly with said signalresponsive relay, said impulse generator comprising an oscillatorycircuit connected in the discharge circuit of said tube adapted uponactivation to generate an oscillatory potential having decrementalamplitude,

a normally non-conductive electron discharge tube having an anode, acathode and a control electrode and havin its control electrodeconnected to said oscillatory circuit, a resistor and condenser networkalso connected in the discharge path of said first-mentioned tube andconnected to the cathode of said second-mentioned tube and having apotential difference time characteristic substantially identical inconfiguration and magnitude with the envelope of said oscillatorypotential for causing said control electrode to reach a predeterminedpotential with respect to said cathode at the amplitude extremes ofalternate half cycles of said oscillatory potential, and means foractivating said first-mentioned tube a predetermined interval after thedeactivation thereof whereby to deactivate said impulse generator.

8. In a telegraph signal repeater for regeneratively repeatingstart-stop telegraph signals, a signal responsive relay, a normallyactivated electron discharge tube adapted to be deactivated by saidrelay upon response thereof to a start impulse of .a telegraph signal,a, signal transmitting relay, a normally inactive impulse generatorrendered active by said electron discharge tube upon the deactivation ofsaid tube for controlling said transmitting relay jointly with saidsignal responsive relay, said impulse generator comprising anoscillatory circuit connected in the discharge circuit of said tube andadapted upon activation to generate an oscillatory potential havingdecremental amplitude, a normally nonconductive electron discharge tubehaving an anode, a cathode and a control electrode and having itscontrol electrode connected to said oscillatory circuit, a resistor andcondenser network also connected in the discharge path of saidfirst-mentioned tube and connected to the cathode of saidsecond-mentioned tube and havin a potential difference timecharacteristic substantially identical in configuration and magnitudewith the envelope of said oscillatory potential for causing said controlelectrode to reach a predetermined potential with respect to saidcathode at the amplitude extremes of alternate half cycles of saidoscillatory potential, and timing means for activating saidfirst-mentioned tube durin reception by said signal responsive relay ofthe stop impulse of a telegraph signal whereby to deactivate saidimpulse generator.

9. In a telegraph signal repeater, a signal responsive relay, a normallyinactive impulse generator, electron discharge means controlled by saidrelay for setting said generator in operation upon the reception of astart signal impulse by the relay, a signal transmitting relay, meanscontrolled jointly by said signal responsive relay and said impulsegenerator for operating said transmitting relay, and means operativewhen a predetermined number of impulses have been generated by saidimpulse generator for conditioning said electron discharge means in amanner to cause said impulse generator to restart its pulsing cycle uponthe reception of the next start signal impulse by said signal responsiverelay.

WILTON T. REA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,133,456 Kinkead Oct. 16, 19382,406,096 Morrison Aug. 20, 1946

